Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching

Pull livepatching updates from Jiri Kosina:

 - remove of our own implementation of architecture-specific relocation
   code and leveraging existing code in the module loader to perform
   arch-dependent work, from Jessica Yu.

   The relevant patches have been acked by Rusty (for module.c) and
   Heiko (for s390).

 - live patching support for ppc64le, which is a joint work of Michael
   Ellerman and Torsten Duwe.  This is coming from topic branch that is
   share between livepatching.git and ppc tree.

 - addition of livepatching documentation from Petr Mladek

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching:
  livepatch: make object/func-walking helpers more robust
  livepatch: Add some basic livepatch documentation
  powerpc/livepatch: Add live patching support on ppc64le
  powerpc/livepatch: Add livepatch stack to struct thread_info
  powerpc/livepatch: Add livepatch header
  livepatch: Allow architectures to specify an alternate ftrace location
  ftrace: Make ftrace_location_range() global
  livepatch: robustify klp_register_patch() API error checking
  Documentation: livepatch: outline Elf format and requirements for patch modules
  livepatch: reuse module loader code to write relocations
  module: s390: keep mod_arch_specific for livepatch modules
  module: preserve Elf information for livepatch modules
  Elf: add livepatch-specific Elf constants

8 files changed, 187 insertions, 9 deletions

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 2fdb73d9198a..a18a0dcd57b7 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -160,6 +160,7 @@ config PPC
 	select HAVE_ARCH_SECCOMP_FILTER
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
 	select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
+	select HAVE_LIVEPATCH if HAVE_DYNAMIC_FTRACE_WITH_REGS
 
 config GENERIC_CSUM
 	def_bool CPU_LITTLE_ENDIAN
@@ -1107,3 +1108,5 @@ config PPC_LIB_RHEAP
 	bool
 
 source "arch/powerpc/kvm/Kconfig"
+
+source "kernel/livepatch/Kconfig"
diff --git a/arch/powerpc/include/asm/livepatch.h b/arch/powerpc/include/asm/livepatch.h
new file mode 100644
index 000000000000..a402f7f94896
--- /dev/null
+++ b/arch/powerpc/include/asm/livepatch.h
@@ -0,0 +1,62 @@
+/*
+ * livepatch.h - powerpc-specific Kernel Live Patching Core
+ *
+ * Copyright (C) 2015-2016, SUSE, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef _ASM_POWERPC_LIVEPATCH_H
+#define _ASM_POWERPC_LIVEPATCH_H
+
+#include <linux/module.h>
+#include <linux/ftrace.h>
+
+#ifdef CONFIG_LIVEPATCH
+static inline int klp_check_compiler_support(void)
+{
+	return 0;
+}
+
+static inline int klp_write_module_reloc(struct module *mod, unsigned long
+		type, unsigned long loc, unsigned long value)
+{
+	/* This requires infrastructure changes; we need the loadinfos. */
+	return -ENOSYS;
+}
+
+static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
+{
+	regs->nip = ip;
+}
+
+#define klp_get_ftrace_location klp_get_ftrace_location
+static inline unsigned long klp_get_ftrace_location(unsigned long faddr)
+{
+	/*
+	 * Live patch works only with -mprofile-kernel on PPC. In this case,
+	 * the ftrace location is always within the first 16 bytes.
+	 */
+	return ftrace_location_range(faddr, faddr + 16);
+}
+
+static inline void klp_init_thread_info(struct thread_info *ti)
+{
+	/* + 1 to account for STACK_END_MAGIC */
+	ti->livepatch_sp = (unsigned long *)(ti + 1) + 1;
+}
+#else
+static void klp_init_thread_info(struct thread_info *ti) { }
+#endif /* CONFIG_LIVEPATCH */
+
+#endif /* _ASM_POWERPC_LIVEPATCH_H */
diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index 7efee4a3240b..8febc3f66d53 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -43,7 +43,9 @@ struct thread_info {
 	int		preempt_count;		/* 0 => preemptable,
 						   <0 => BUG */
 	unsigned long	local_flags;		/* private flags for thread */
-
+#ifdef CONFIG_LIVEPATCH
+	unsigned long *livepatch_sp;
+#endif
 	/* low level flags - has atomic operations done on it */
 	unsigned long	flags ____cacheline_aligned_in_smp;
 };
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 0d0183d3180a..c9370d4e36bd 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -86,6 +86,10 @@ int main(void)
 	DEFINE(KSP_LIMIT, offsetof(struct thread_struct, ksp_limit));
 #endif /* CONFIG_PPC64 */
 
+#ifdef CONFIG_LIVEPATCH
+	DEFINE(TI_livepatch_sp, offsetof(struct thread_info, livepatch_sp));
+#endif
+
 	DEFINE(KSP, offsetof(struct thread_struct, ksp));
 	DEFINE(PT_REGS, offsetof(struct thread_struct, regs));
 #ifdef CONFIG_BOOKE
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 9916d150b28c..39a79c89a4b6 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -20,6 +20,7 @@
 
 #include <linux/errno.h>
 #include <linux/err.h>
+#include <linux/magic.h>
 #include <asm/unistd.h>
 #include <asm/processor.h>
 #include <asm/page.h>
@@ -1248,6 +1249,9 @@ _GLOBAL(ftrace_caller)
 	addi	r3,r3,function_trace_op@toc@l
 	ld	r5,0(r3)
 
+#ifdef CONFIG_LIVEPATCH
+	mr	r14,r7		/* remember old NIP */
+#endif
 	/* Calculate ip from nip-4 into r3 for call below */
 	subi    r3, r7, MCOUNT_INSN_SIZE
 
@@ -1272,6 +1276,9 @@ ftrace_call:
 	/* Load ctr with the possibly modified NIP */
 	ld	r3, _NIP(r1)
 	mtctr	r3
+#ifdef CONFIG_LIVEPATCH
+	cmpd	r14,r3		/* has NIP been altered? */
+#endif
 
 	/* Restore gprs */
 	REST_8GPRS(0,r1)
@@ -1289,6 +1296,11 @@ ftrace_call:
 	ld	r0, LRSAVE(r1)
 	mtlr	r0
 
+#ifdef CONFIG_LIVEPATCH
+        /* Based on the cmpd above, if the NIP was altered handle livepatch */
+	bne-	livepatch_handler
+#endif
+
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	stdu	r1, -112(r1)
 .globl ftrace_graph_call
@@ -1305,6 +1317,91 @@ _GLOBAL(ftrace_graph_stub)
 
 _GLOBAL(ftrace_stub)
 	blr
+
+#ifdef CONFIG_LIVEPATCH
+	/*
+	 * This function runs in the mcount context, between two functions. As
+	 * such it can only clobber registers which are volatile and used in
+	 * function linkage.
+	 *
+	 * We get here when a function A, calls another function B, but B has
+	 * been live patched with a new function C.
+	 *
+	 * On entry:
+	 *  - we have no stack frame and can not allocate one
+	 *  - LR points back to the original caller (in A)
+	 *  - CTR holds the new NIP in C
+	 *  - r0 & r12 are free
+	 *
+	 * r0 can't be used as the base register for a DS-form load or store, so
+	 * we temporarily shuffle r1 (stack pointer) into r0 and then put it back.
+	 */
+livepatch_handler:
+	CURRENT_THREAD_INFO(r12, r1)
+
+	/* Save stack pointer into r0 */
+	mr	r0, r1
+
+	/* Allocate 3 x 8 bytes */
+	ld	r1, TI_livepatch_sp(r12)
+	addi	r1, r1, 24
+	std	r1, TI_livepatch_sp(r12)
+
+	/* Save toc & real LR on livepatch stack */
+	std	r2,  -24(r1)
+	mflr	r12
+	std	r12, -16(r1)
+
+	/* Store stack end marker */
+	lis     r12, STACK_END_MAGIC@h
+	ori     r12, r12, STACK_END_MAGIC@l
+	std	r12, -8(r1)
+
+	/* Restore real stack pointer */
+	mr	r1, r0
+
+	/* Put ctr in r12 for global entry and branch there */
+	mfctr	r12
+	bctrl
+
+	/*
+	 * Now we are returning from the patched function to the original
+	 * caller A. We are free to use r0 and r12, and we can use r2 until we
+	 * restore it.
+	 */
+
+	CURRENT_THREAD_INFO(r12, r1)
+
+	/* Save stack pointer into r0 */
+	mr	r0, r1
+
+	ld	r1, TI_livepatch_sp(r12)
+
+	/* Check stack marker hasn't been trashed */
+	lis     r2,  STACK_END_MAGIC@h
+	ori     r2,  r2, STACK_END_MAGIC@l
+	ld	r12, -8(r1)
+1:	tdne	r12, r2
+	EMIT_BUG_ENTRY 1b, __FILE__, __LINE__ - 1, 0
+
+	/* Restore LR & toc from livepatch stack */
+	ld	r12, -16(r1)
+	mtlr	r12
+	ld	r2,  -24(r1)
+
+	/* Pop livepatch stack frame */
+	CURRENT_THREAD_INFO(r12, r0)
+	subi	r1, r1, 24
+	std	r1, TI_livepatch_sp(r12)
+
+	/* Restore real stack pointer */
+	mr	r1, r0
+
+	/* Return to original caller of live patched function */
+	blr
+#endif
+
+
 #else
 _GLOBAL_TOC(_mcount)
 	/* Taken from output of objdump from lib64/glibc */
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 290559df1e8b..3cb46a3b1de7 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -66,6 +66,7 @@
 #include <asm/udbg.h>
 #include <asm/smp.h>
 #include <asm/debug.h>
+#include <asm/livepatch.h>
 
 #ifdef CONFIG_PPC64
 #include <asm/paca.h>
@@ -607,10 +608,12 @@ void irq_ctx_init(void)
 		memset((void *)softirq_ctx[i], 0, THREAD_SIZE);
 		tp = softirq_ctx[i];
 		tp->cpu = i;
+		klp_init_thread_info(tp);
 
 		memset((void *)hardirq_ctx[i], 0, THREAD_SIZE);
 		tp = hardirq_ctx[i];
 		tp->cpu = i;
+		klp_init_thread_info(tp);
 	}
 }
 
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index b8500b4ac7fe..2a9280b945e0 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -55,6 +55,8 @@
 #include <asm/firmware.h>
 #endif
 #include <asm/code-patching.h>
+#include <asm/livepatch.h>
+
 #include <linux/kprobes.h>
 #include <linux/kdebug.h>
 
@@ -1400,13 +1402,15 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
 	extern void ret_from_kernel_thread(void);
 	void (*f)(void);
 	unsigned long sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
+	struct thread_info *ti = task_thread_info(p);
+
+	klp_init_thread_info(ti);
 
 	/* Copy registers */
 	sp -= sizeof(struct pt_regs);
 	childregs = (struct pt_regs *) sp;
 	if (unlikely(p->flags & PF_KTHREAD)) {
 		/* kernel thread */
-		struct thread_info *ti = (void *)task_stack_page(p);
 		memset(childregs, 0, sizeof(struct pt_regs));
 		childregs->gpr[1] = sp + sizeof(struct pt_regs);
 		/* function */
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index f98be8383a39..96d4a2b23d0f 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -69,6 +69,7 @@
 #include <asm/kvm_ppc.h>
 #include <asm/hugetlb.h>
 #include <asm/epapr_hcalls.h>
+#include <asm/livepatch.h>
 
 #ifdef DEBUG
 #define DBG(fmt...) udbg_printf(fmt)
@@ -667,16 +668,16 @@ static void __init emergency_stack_init(void)
 	limit = min(safe_stack_limit(), ppc64_rma_size);
 
 	for_each_possible_cpu(i) {
-		unsigned long sp;
-		sp  = memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit);
-		sp += THREAD_SIZE;
-		paca[i].emergency_sp = __va(sp);
+		struct thread_info *ti;
+		ti = __va(memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit));
+		klp_init_thread_info(ti);
+		paca[i].emergency_sp = (void *)ti + THREAD_SIZE;
 
 #ifdef CONFIG_PPC_BOOK3S_64
 		/* emergency stack for machine check exception handling. */
-		sp  = memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit);
-		sp += THREAD_SIZE;
-		paca[i].mc_emergency_sp = __va(sp);
+		ti = __va(memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit));
+		klp_init_thread_info(ti);
+		paca[i].mc_emergency_sp = (void *)ti + THREAD_SIZE;
 #endif
 	}
 }
@@ -700,6 +701,8 @@ void __init setup_arch(char **cmdline_p)
 	if (ppc_md.panic)
 		setup_panic();
 
+	klp_init_thread_info(&init_thread_info);
+
 	init_mm.start_code = (unsigned long)_stext;
 	init_mm.end_code = (unsigned long) _etext;
 	init_mm.end_data = (unsigned long) _edata;